Quantitative aspects of Mn‐activated cathodoluminescence of natural and synthetic aragonite

Abstract

The cathodoluminescence analyses of the trigonal carbonates calcite and dolomite have been applied intensively in sedimentary petrology for a long time and the properties of these minerals are well-known, but much less attention has been paid to aragonite. In this study, the cathodoluminescence behaviour and the trace element composition of natural and synthetic aragonite have been studied employing trace element analyses (proton induced X-ray emission) and luminescence spectroscopy. Aragonite doped with Mn 2+ has been synthesized in a NH 4 + -Mg 2+ -Ca 2+ -Cl ) solution in contact with a CO 2 -H 2 O-NH 3 atmosphere. The low effective distribution coefficients indicate a rapid growth of the crystals of millimetre size which occurred within hours or days. The natural aragonite samples contain Mn, Fe and Sr in different concentrations. The Mn-bearing aragonites exhibit a bright green luminescence which is caused by a strong emission band at 575 nm with a half-width of about 84 nm. The luminescence intensity shows a strong positive correlation with Mn in aragonite when Fe and Mn do not exceed 2000 p.p.m. The intensity is depressed if the concentration of these elements exceeds the critical values. In the shell of a recent Unio sp., the luminescence intensity deviates from the linear correlation, although the trace element contents are not too high; this is probably an effect of quenching by organic material between the crystallites of the biogenic aragonite.

Late Miocene Seasonal to Subdecadal Climate Variability in the Indo-West Pacific (East Kalimantan, Indonesia) Preserved in Giant Clams

“…Relatively large cations like Sr 2+ and Ba 2+ substitute better for Ca 2+ in the orthorhombic aragonite structure, while smaller ions such as Mg 2+ show affinity to the rhombohedral calcite lattice (Gotte and Richter 2009). The behavior of Mg and Sr in the different carbonate polymorphs was documented by Harriss (1965), who compiled analyses of molluscan shell material of 95 different species.…”

“…5). Nonluminescent to blue luminescent colors in biogenic carbonates have been interpreted as an indicator for excellent preservation (Barbin et al 1995;Gotte and Richter 2009;Brand et al 2012;Wendler et al 2012). The intrinsic luminescence is due to the absence of Mn 2+ , which is a major luminescence activator in carbonates (Langlet et al 2006).…”

“…The intrinsic luminescence is due to the absence of Mn 2+ , which is a major luminescence activator in carbonates (Langlet et al 2006). Elevated Mn 2+ concentrations in aragonite result in yellowgreen luminescing aragonite (Barbin et al 1995;Gotte and Richter 2009). The single green band observed in BW4B (Fig.…”

New insights into geochemical behaviour in ancient marine carbonates (Upper Jurassic Ammonitico Rosso): Novel proxies for interpreting sea‐level dynamics and palaeoceanography

“…; e.g. Machel, ; Götte & Richter, ); or (iii) the contribution of Fe 3+ or Mn 4+ , reported in the literature as intrinsic luminescence activators (e.g. Götze et al ., ; MacRae & Wilson, and de Rafélis et al ., , respectively).…”

Geochemical evidence for sediment provenance in mudstones and fossil‐poor wackestones (Upper Jurassic, Majorca Island)

“…Yet, quenching thresholds for Fe 2+ vary from 30–60 p.p.m to 3000–4000 p.p.m (e.g. Machel, 2000; Götte and Richter, 2009). Regarding the samples investigated here, the obtained Mn concentrations show pronounced peaks up to 1500 p.p.m, which are also recognized on coeval sections (Coimbra et al.…”